Electropneumatic tool.



A. PALMROS. ELEGTROPNEUMATIO TOOL. APPLICATION FILED 1 n0 .13, 1904.

Patented Apr. 2, 1912.

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A. PALM-ROS. ELECTROPNEUMA'TIG IIOOL. APPLIOATIQN FILED DLEO.18. 1904.

Patented Apr. 2, 1912.

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A. PALMROS.

ELEGTROPNEUMATIG TOOL. APPLICATION FILED DEO.13, 1904.

Patented Apr.-2, 1912.

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Attorneys A. PALMROS. ELECTROPNEUMATIG TOOL. APPLICATION FILED DEO.13,1904. Patented Apr. 2; 1912.} x

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ELEGTROPNEUMATIG TOOL.

APPLICATION FILED-D3013, 1904.

. Patented Apr. 2, 1912;

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ELEOTROPNEUMATIC TOOL.

APPLICATION FILED. DBO.13.'1904.

Patented Apr. 2, 1912.

6 SHEETS-SHEET 6.

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COLUMBIA PLANOGRA'Pi-i co., WASHINGTON, D. Cl,

UNITED STATES PATENT OFFICE.

ALEXANDER PALMROS, OF FAIRMONT, WEST VIRGINIA, ASSIGNOR TO THE PNETIM-ELECTRIC MACHINE COMPANY, OF SYRACUSE, NEW YORK, A CORPORATION OF NEWYORK.

ELECTROPNEUMATIG TOOL.

Specification 0: Letters Patent.

Patented Apr. 2, 1912.

Application filed December 13, 1904. Serial No. 236,738.

To all whom it may concern:

Be it known that I, ALEXANDER PALMRos, a citizen of Finland, and aresident of Fairmont, in the county of Marion and State of WestVirginia, have invented certain new and useful Improvements inElectropneumatic Tools, of which the following is a specification.

My invention relates more particularly to tools performing their work bypercussion, and of the same general type as that described in U. S.Letters Patent No. 761,602 granted May 31, 1904 to Alexander Palmros andCarson W. Damron, and my invention consists in certain novel features ofconstruction, hereinafter fully described and particularly pointed outin the claims.

In my present machine, I retain the ad vantages incident topermittingthe tool to be driven forward, by the expansion of a pressuremedium automatically maintained at high efliciency by an auxiliary ormotor driven pump, as set forth in my patent above mentioned, and at thesame time, I greatly increase the efi'ectiveness of the blow. That is tosay, I'employ the driving piston as a pumping piston, but the pumpingaction takes place only during a small part of the forward stroke of thetool, and only after the full momentum of the parts has developed and ata period when a cushioning eifect is desired; and the reinforcing air tobe delivered to the compresion sp. ce is forced into a by-pass so thatit can enter the compression space when the pressure is sufficientlyreduced therein to require it; the pumping action is further preventedfrom materially reducing the impact stroke by the fact that the toolwhile free to drive ahead under the expanding pressure medium, is stillbeing driven by the motor, for which reason the pumping action isindependent of instead of being a burden upon the expanding force whichdevelops the working stroke of the piston; and the eifectiveness of thestroke is further increased by the combined effect of two additionaldistinct agencies, namely, the momentum of the armature acting as a flywheel, and the con tinued driving force ofthe field acting on thearmature, notwithstanding the latter, by its peculiar relation to itsdriving member is free to race ahead under the expanding force of thepressure medium; that is to say, inthe novel combination of a primemover, preferably an electric motor, whose driven member is capable ofracing ahead or quickening its movement during the impact stroke of themachine, while still receiving the driving force which normally impelsit and the constantly connected reciprocating tool piston whichcompresses the pressure me dium on its rearward stroke and is accelerated by the expansion of said medium onthe forward stroke, the drivingmember in this combination, actsin supplement of, or as an auxiliary tothe expanding pressure-medium, both in the acceleration of the forwardstroke, and in the storing up of work (due to increased mass ofconnected moving elements) to be expended in the impact.

It is true that the fly wheel effect is not transmitted directly to thedrill, but indirectly through piston connection which yields slightly atthe instant of first impact, to relieve the shock on the machine, butthe construction is such that the body of air through which thisreinforce of blow is exerted is kept supplied in a dense condition andthe effect is therefore peculiarly advantageous for the excavation ofmany materials, where a prolonged crushing blow is most effective. Thatis to say, while there is a slight yield at first, the blow is followedup by the additional force before the material attacked can recover fromthe first load impressed upon it and the penetration is greater thanresults from a construction Where the first shock is transmitted to andtends to arrest the entire train of driving parts.

In the accompanying drawings forming part of this specification, Figures1 and 1 show a vertical axial section, partly in elevation, of a coalmining machine in which my invention is embodied by way of illustration,the working end of the bit, which may be of any usual construction,being broken away. Fig. 2 is a rear elevation of the same on an enlargedscale, the gear casing being in section in the vertical transverse planeof the main gear spindle. Fig. 3 is a plan view of the gear seen frombelow with its casing in section, and the "retracting rod with itssliding head shown in dotted lines. Figs. 4: and 5 are transversesections taken respectively on the lines IVIV and VV, Figs. 11 lookingforward. Fig. 6 is a front elevation of the machine with the cylinder insection on the line VIVI Fig. 1, and the upper part of the motor casingbroken away. Figs. 7 and 8 are transverse sections taken respectively onthe lines VIIVII and VHF-VIII Fig. 1. Figs. 9 and 10 are axial sectionsshowing two other structural embodiments of the pneumatic features of myinvention. Fig. 11, is an axial sectional view showing the applicationof my invention to that class of tools, such as riveting tools,chippers, stone drills and the like, in which the working end is held incontact with the work during use while reciprocation is imparted to thepercussive member to develop the driving impact. Fi 12 is a sectionalview of another constructional embodiment of the invention.

The general arrangement of the machine herein adopted for illustratingthe principles of my invention, is such as to reduce the size anddimensions to a minimum and the exterior lines to a form which isconvenient to the position that mustbe assumed by the operator, andwhich facilitates manipulation. Vith these objects in view, the frame orcasing of the machine as will hereinafter appear, is divided into threemain parts, namely, the intermediate main cylinder A directly mounted onthe wheels and carrying the means for developing and utilizing the fluidpressure, the forward plunger guide carrying the plunger to be actuated,and the rear gear and motor casings carrying the prime actuating andtransmitting mechanisms which front and rear members are fitted to theends of the main cylinder and tied together and secured to said cylinderby tie rods. To economize space in this general arrangement, the motor 1having armature 2 is mounted in a casing 3 forming the upper forwardpart of the casings C, while the motor shaft 4 has its lower hearing 5in a spider in the upper wall of the gear casing and terminates in apinion 6 within said casing. A large reduction gear 7 mounted upon aspindle, 8, transverse to the reciprocating member of the machine, andextending vertically, in rear of the motor, into a bearing 9 on themotor casing, receives motion from motor pinion 6, and transmits saidmotion through an eccentric pin 10. In order to convert the throw of theeccentric pin 10 into a right-line movement coincident with the axis ofthe reciprocating member, said pin carries a crank pinion 11 having awrist pin 12 which connects with the crosshead 13 of the reciprocatingmember, and whose throw, due to the rotation of pinion 11, is exactlyhalf the stroke to be imparted to the cross-head, while said pinion 11,by

meshing with fixed circular rack 14, receives one rotation about itscenter, for each revolution of its center with main gear 7.

To develop the stroke, cross-head 13 is connected to a retracting bar15, and slides between adjustable under cut guides 16, which retractingbar 15 works through the packing gland 17, and connects at 19 with themain piston 20 which operates in the cylindrical bore 21, to compressair or other fluid pressure medium on its rearward stroke and to beimpelled by said fluid pressure on its forward stroke and made todeliver a forcible blow through the plunger 22 controlled by saidpiston. Plunger 22 is guided in the forward extension or casin 23, andin the present illustrative embodiment, extends beyond said casing toreceive any suitable bit socket 24, and bit 25. Exhaust port 26 per mitsescape of air from in front of piston 20, during the greater portion ofits forward stroke, and a valved intake port 27 supplies air to overcomethe vacuum during the first part of the rearward stroke.

To insure a full stroke of the machine, it will be observed that thedriving motor is continuously in fixed driving connection with thepiston 20 so that the piston must move to the end of its forward strokeat each revolution of the driving gear. This continuously fixed drivingconnection permits the forward stroke under the influence of the fluidpressure that has been developed by the inward stroke this being due tothe driven member of the motor, in this case the armature, racing aheadof its driving member and yet being at all times in such relation to thelatter member that the driving influence will be exerted the instant theexpanding fluid pressure ceases to race the iston.

lVhile I have shown an electric motor and prefer to use this type ofdriving power, it is obvious that other known forms of prime movers oreven various forms of driving connections from exterior sources of powermight be utilized to actuate the machine and still maintain thedescribed relations between the driving power and the reciprocatingmember.

To cushion the tool, avoid arresting the forward stroke of the mainpiston by an obstruction to the plunger and to avoid the running forwardof the main piston in the event of such an obstruction, the plunger 22is connected to the piston 20 not directly but indirectly through themedium of a cushioning chamber 28 and piston 29 working therein, so thatwhen the plunger strikes a hard place in the coal (for instance) whichobstructs its advancement to the full extent of the stroke of themachine, main piston 20 may continue its forward movement, compressingair behind the piston 29, and when the compression stroke of main piston20 binds in the mineral and resists retractionv after being thusobstructed in its forward movement, the main piston 20 will moverearward independently of plunger 22 until piston 29 reaches the forwardend of the cushioning chamber which acts as a shoulder, and after themomentum of the rearward stroke has materially developed, will draw thebit from the mineral.

30 represents a packing gland for the plunger 22 and 31 is a packing andcushioning ring placed between said gland and the piston 29.

In order to maintain sufficient pressure in the cushioning chamber 28,said chamber communicates through passages 32 with the main cylinder 21.This may occur when said passages reach the enlarged portion of the maincylinder on the rearward stroke of the piston as shown "in Fig. 1 or itmay occur when the annular groove 33 communicating wit-h passages 32,passes a recess 34 in cylinder 21 of suflicient length to establishmomentary communication between the groove 33 and the pressure spacebehind the.

main piston, as shown in Figs. 9 and 12.; or the same effect maybeproducedby having a stem 38 connected with thepiston 29 work ing in abore in the retractor bar 15, having a port 39 communicating withcushion chamber 28, and ports 40 which communicate with a transversebore 41 leading to the pressure space behind the main piston, so thatwhenever the pressure in the chamber 28 becomes so far reduced that itwill not drive the plunger to its full. stroke, and main piston 20 movesforward relatively to the plunger 22, the passage 41, 40, 38, 39 ,'isopened to restore pressure to the chamber 28. According to theconstruction shown in Fig. 1, a valved passage 35 permits the escape ofair in front of piston 29 as it returns to its seat, the position ofthis passsage, however, being such that some air is trapped to reducethe blow on the forward head of chamber 28; also a port 32 may beprovided in chamber 28 with a spring loaded valve of such resistancethat it will resist the desired pressure in chamber 28, but will openunder excessive pressure therein and thus maintain the cushioning effecton the plunger 22at precisely the desired degree. In Figs. 9 and 10,these ports marked 35*, are duplicated and shown without a valve. InFig. 1 the port 32 is in tersected by a longitudinal bore 36 in which islocated an adjustable valve 37 to regulate the opening 32 andconsequently the inlet of pressure to chamber 28.

22 represents a cushioned shoulder on plunger 22. Should the piston 29occupy a rearward position in chamber 28 when the machine makes itsrearward stroke, this shoulder 22 will impinge the abutment 22 andarresting the rearward stroke of the plunger, will insure full space inrear of piston 29, in chamber 28; the cushioning body of air trapped infront of piston 29, in consequence of the position of valved passage 35,serves to prevent shock on the parts at this time.

s From the foregoing description, it will be observed that theretracting and striking members or the opposed faces thereof,

through means of which one exerts its influence over the other, areseparated by a body of air through which such control is exerted. 7

To maintain initial pressure on the compression side of the main piston,the exhaust port 26 is so disposed and other ports are so provided thatthe terminal portion of the forward stroke of the main piston 20 acts asa pump and delivers pressure to its rear side, at the same timecushioning said main piston and greatly relieving the shock on theactuating mechanism of the tool.

In Figs. '1 and 1, 43 represents a longitudinal passage in the cylinder21 which communicates through a valved port 42 with the forward end ofcylinder 21 and discharging again into the cylinder 21 at a point thatwill be behind piston 20 when it reaches its forward limit. In order toavoid loss of pressure, the passage 43 is made short in Figs. 1, 1 butthis passage may be made to extend the full length of cylinder 21 asshown at 43 43 and 43 in Figs. 9 and 10 respectively and, as shown inFigs. 9 and 10, it may be provided at its rear or discharge end with anadditional check valve 44 or 44 so as to avoid the necessity ofcompressing the full capacity of the passage at each stroke, it beingobvious that as the piston recedes from the valve 42,both this valve andvalve 44 or 44 will close and retain a column of air under the fullpressure developed by the priming stroke of the piston, so that eachtime initial pressure is supplied through the passage 43, 43*, 43 43loss due to the extent of the passage will be avoided.

Regulating the initial pressure is accomplished with great accuracy bymeans of a relief valve 45, 45 or 45" Figs. 4, 9 and 10, the tension ofwhose spring may be readily regulated. Since the pressure developed bythe primary stroke of the main piston depends upon the resistance of itsrelief valve, it follows that the initial pressure delivered to thecompression side of the main piston, and consequently the force of thestroke of the machine, may be regulated at will by merely increasing ordiminishing the tension of the closing spring of the valve 45.

Riveters, chippers, etc., (Fig. 11) may be constructed according to myinvention, by having the fixed bit 46 in the path of the plunger 22, theremaining portions of the machine being as already described and themachine having a handle 3" on its casing 3 External motors might also beemployed as suggested by the crank 1 cross-head 13 and retractor 15 inthe casing 18 48 represents the wheels which are longitudinallyadjustable through connections 49 of known construction.

50 represents the tie-rods passing through ears 51, 52 on the rear andforward casings and binding these parts firmly to the main cylinder 21.

Having thus described my invention, the following is what 1 claim as newtherein and desire to secure by Letters Patent:

1. In a power driven reciprocating tool, the combination of a cylinder,a reciprocating member having a piston working in said cylinder andcompressing an expansible medium on its rearward stroke and driven bysaid expansible medium on its forward stroke, and an electric motorhaving its armature in continuously fixed driving connection with thereciprocating member and free to rotate independently of the motor powerand race ahead under the influence of the compressed medium duringdelivery of the stroke of the machine.

2. The combination with a motor comprising a driving stationary part anda rotating part, capable of racing ahead of the driving force, of areciprocating member having continuously fixed driving connection withthe rotating part of the motor, and means in which power is storedduring one stroke of the reciprocating member, acting 011 the rotarypart of the member to cause said part to race ahead of its drivingforce.

3. The combination with an electric mo tor, of a reciprocating memberhaving continuously fixed driving connection with the armature, andmeans in which power is stored during one stroke of the reciprocatingmember, acting on the armature to cause it to race ahead of its drivingforce.

1. The combination with a retracting and a striking member, of means constructed to store air compressed on the retracting stroke of theretracting member, and means utilizing said compressed air to cause theimpact of the striking element, the retracting and the striking elementsbeing separated by an air space through which one exerts control overthe other.

The combination with a motor comprising a driving stationary part and arotating part, capable of racing ahead of the driving force, of areciprocating member having continuously fixed driving connection withthe rotating part of the motor, means in which power is stored duringone stroke of the reciprocating member, acting on the rotary part of themember to cause said part to race ahead of its driving force, and ayielding connection interposed in said reciprocating member.

6. The combination with an electric motor, of a reciprocating memberhaving continuously fixed driving connection with the armature, means inwhich power is stored during one stroke of the reciprocating memberacting on the armature to cause it to race ahead of its driving force,and a yielding connection interposed in said reciprocating member.

7. The combination with a motor comprising a driving stationary part anda rotating part, capable of racing ahead of the driving force, of areciprocating member having continuously fixed driving connection withthe rotating part of the motor, means in which power is stored duringone stroke of the reciprocating member, acting on the rotary part of themember to cause said part to race ahead of its driving force, and ayielding connection interposed in said reciprocating member comprising acylinder containing a yielding medium and a piston against which theyielding medium exerts its force.

8. In a power driven reciprocating tool, the combination of areciprocating member, a cylinder and piston by which an expan siblemedium is compressed by the rearward stroke of the reciprocating memberand through which it exerts its expanding force in the forward stroke ofthe reciprocating member, a cylinder and piston by which a yieldingconnection is made between the working end of the tool and its actuatingpower and means whereby pressure developed in the reciprocation of thetool, is communicated to the yielding connection cylinder to maintainpressure therein and hold its piston in working position.

9. In a fluid pressure tool, having a piston working in a cylinder,compressing a fluid on its rearward stroke and utilizing said fluidaressure on its forward stroke; a yield ing connection between thepiston and the tool operating part, consisting of a yielding connectioncylinder communicating with the cylinder first named and receivingpressure therefrom and containing a piston carried by the tool operatingpart, and means con trolling the communications between the yieldingconnection cylinder and the cylinder first named, to regulate thepressure communicated to the yielding connection cylinder and therebyregulate resistance of the yielding connection.

10. In a power driven reciprocating tool, the combination of areciprocating member, a cylinder, a piston, one end of which isconnected with the reciprocating member and by which an expansiblemedium is com-' pressed by the retraction of the reciprocating memberand exerts its expansible force during the opposite movement of thereciprocating member, a second cylinder, a piston interposed as ayielding connection between a portion of the reciprocating memberand itsworking end, and connections whereby pressure developed by the movementof the reciprocating member is communicated to the yielding connectioncylinder.

11. In a power driven fluid pressure tool, the combination of a plungerfor operating the tool, a main cylinder in which the plunger works, amain piston, means for retracting the piston to compress an expansiblemedium in the main cylinder for use in driving the main piston forward,a cylinder constructed within the main piston, a yield-' ing connectionpiston connected with the plunger and working in the cylinder within themain piston, and connections, communicating pressure from the maincylinder to the cylinder within the main piston,whereby the drivingpower is imparted to the plunger through fluid pressure. 1

12. In'a power driven pressure tool, the combination of a plunger, amain cylinder in which said plunger works and a main piston by which theplunger is reciprocated; the piston on the plunger, by which the plungeris connected to the main piston said piston on the plunger working in acylinder within the main piston, and said cylinder within the mainpiston having communication with the main cylinder at intervals tosupply pressure in the cylinder within the piston and having a reliefvalve opening under excessive resistance to the plunger.

13. The herein described yielding connection consisting of a cylinderand piston, means introducing fluid under pressure hehind the piston andmeans permitting escape of air in front of the piston located to trap acushioning body of air at such point.

14. In a power driven fluid pressure tool, in which the rearwardstroke'develops fluid pressure that exerts its force on the forwardstroke, a yielding connection through which the .tool performs its work,consisting of a cylinder and'piston, the former of which is providedwith a passage in rear of the yielding connection piston receivingpressure'developed by the rear stroke.

15. In combination with an actuating member, a plunger to be actuated,and a yielding connection cylinder and piston through which the plungeris actuated; a shoulder on the plunger, and an abutment on a part fixedrelatively to the plunger impinged by said shoulder, on the rearwardstroke of the tool, when the yielding connection piston remains rearwardin its cyl-V inder.

16. In a power driven fluid pressure tool, the combination of a maincylinder, a main piston having means for moving 1t in one direction inthe main cylinder to develop let valve communicating with its forward,

end to permit return of the plunger to normal position relatively to themain piston.

17 In a power driven fluid pressure tool, the combination of a motor, areciprocating member with which the motor has suitable connection, amain cylinder, and a main piston carried by the reciprocating member, bywhich fluid pressure is developed in the rearward movement of thereciprocating member and through which such fluid pressure is exerted todrive the reciprocating member forward; said main cylinder and mainpiston being provided with ports and passages through which the mainpiston develops pressure in the main cylinder in front of the mainpiston, during the terminal portion of its forward stroke and deliverssaid pressure to the main cylinder in the rear of the main piston, tomaintain an initial pressure on the rear side of the piston.

18. In a power driven fluid pressure tool, the combination of a maincylinder and piston, a reciprocating member producing relative movementbetween said piston and cylinder in its rearward stroke and receivingdriving power from such pressure during its forward stroke, a motorhaving continuous connection with the reciprocating member and insuringthe completion of its forward stroke, and means whereby the terminalportion of the forward stroke of the main piston develops and deliversan initial pressure to the rear of said piston.

19. In a fluid pressure tool of the character described, the combinationof a main cylinder,-a main piston working in said cylinder to compressfluid therein on its rearward stroke and to utilize the expansible forceof said fluid on its forward stroke, said cylinder having an outletpermitting escape of the pressure medium in advance of the piston duringa part of its forward stroke, means communicating the pressure developedby the terminal portion of said forward stroke to the rear of thepiston, a check valve to prevent return of said pressure during therearward compression stroke of the piston and a valve opening into theforward end of the mainicylinder under external pressure during the rearward stroke of the piston.

20. In a fluid pressure tool of the character described, the combinationof a main cylinder, a main piston working in said cyl inder to compressfluid therein on its rear ward stroke and to utilize the expansibleforce of said fluid on its forward stroke, said cylinder having anoutlet permitting escape of the pressure medium in advance of the pistonduring a part of its forward stroke, means communicating the pressuredeveloped by the terminal portion of said forward stroke to the rear ofthe piston, a check valve to prevent return of said pressure during therearward compression stroke of thepiston, a valve opening into theforward end of the main cylinder under external pressure during therearward stroke of the piston and a relief valve opening under excessivepressure developed by said terminal portion of the forward stroke of thepiston.

21. In a fluid pressure tool of the character described, the combinationof a main cylinder, a main piston working in said cylinder to compressfluid therein on its rearward stroke and to utilize the expansible forceof said fluid on its forward stroke, said cylinder having an outletpermitting escape of the pressure medium in advance of the piston duringa part of its forward stroke, means communicating the pressure developedby the terminal portion of said forward stroke to the rear of thepiston, a check valve to prevent return of said pressure during therearward compression stroke of the piston, a valve opening into theforward end of the main cylinder under eX- ternal pressure during therearward stroke of the piston and a relief valve opening under excessivepressure developed by said terminal portion of the forward stroke of thepiston; said relief valve having means for regulating its resistance toopening, whereby the pressure developed in front of the piston at theend of its forward stroke and consequently the initial pressuredelivered in rear of the main piston, may be regulated at will.

22. In a tool of the character described in which the piston compressesat the end of its forward stroke to supply initial pressure in rear ofthe piston, the combination of a cylinder, said cylinder having apassage extending from one end of the cylinder to the other and checkvalves in said passage near its ends whereby pressure is maintained insaid passage for the greater portion of its length to prevent loss ateach stroke.

23. The combination with the suitably housed piston, of means forstoring a compressed fluid upon one face of said piston to drive thepiston in one direction, means for furnishing communication between bothfaces of said piston to lead the fluid from one face to the other, and avalve controlling said communication, opening during the drivingmovement and closure during the compression movement.

24. The combination with the motor, of a suitably housed piston moved inone direction by the motor, means storing a fluid compressed by thepiston during such movement, to drive the piston in the other direction,means for furnishing communication between both faces of said piston,and a valve controlling such communication, opening during the drivingmovement and 010s ing during the compression movement.

25. The combination with a suitably housed piston, of means confining afluid and subjecting it to the compression action of one side of saidpiston, means for furnishing a communication between opposite sides ofthe piston, and a valve controlling said communication, opening duringone movement of the piston and closing during the other movement of thepiston.

26. The combination with a piston, of a cylinder having an outlet toatmosphere near one end and cooperating with said piston to cause thecompression of a fluid near the opposite end of the cylinder, and avalved communication between the compression end of the cylinder and theother end beyond the outlet.

27. The combination with a piston, of a cylinder in which the pistonworks formed so as to permit the piston to compress a fluid at one endthereof, and having an outlet to atmosphere near its other end, and avalved communication between the compression end and other end beyondthe out let, whereby the piston is permitted to at first move freelyunder the action of the compressed fluid and then partially charge thecompression space.

28. The combination with a motor, and a piston constantly driven by themotor, of a cylinder in which the piston works, formed so as to permitthe piston to compress a fluid at one end thereof and having an outletto atmosphere near its other end, and a valved communication between thecompression end and the other end beyond the outlet.

29. In a fluid pressure tool, a compression chamber in which fluid iscompressed during the retracting stroke of the tool, a

[compressing walls of the pistons from the compression side of thedriving piston.

31. The combination of suitably housed and tool-bearing pistons, meanswhereby one piston retracts the other after delivery of the stroke,means for storing a fluid compressed by the compressing piston, andmeans for admitting'fluid between opposed walls of the pistons from thecompression side of the compressing piston, during the compressingmovement.

32. The combination with a cylinder, of a piston movable therein, tocompress a fluid on one stroke, means for delivering fluid from one sideof the piston to the other during the other stroke of the piston, and atool operated by the compressed fluid.

33. The combination with a motor of an element constantly driven by themotor, a tool carrying element, means for causing the tool carryingelement to move with a percussive'stroke, and means confining a body ofair between the tool carrying element and the motor-driven element tocause the tool to penetrate a material after the material has beenfractured by the percussive stroke.

34. The combination with a motor, of a motor driven element, a toolcarrying element, a yielding connection between said elements, and meansfor causing the tool carrying element to deliver a percussive stroke.

. 35. The combination with a motor, of a motor driven element, a toolcarrying element, a yielding connection between said elements, means forcausing the tool carrying element to deliver a percussive stroke, andmeans establishing retracting relation between the elements.

36. In a pressure driven percussive tool, the combination of a drivingelement, a tool carrying element, means confining a body of air betweenopposed walls of said elements, means causing the compression of a fluidto develop the tool driving pressure, upon the movement of the drivingelement in one direction, and means for delivering a portion of saidcompressed fluid to the space between the opposed walls of the elementsto keep up the pressure of thebody of air therebetween. i

37. In a fluid pressure driven tool, the combination of a reciprocatingtool carrying member mounted to have a retracting stroke in onedirection and a percussion stroke in the opposite direction, a drivingmeans to exert driving power upon said reciprocating tool carryingmember during bot-h its retracting and precussion strokes, and meansconstructed to develop fluidpressure during the retracting stroke of thereciprocating tool carrying member and to cause the pressure thusdeveloped, to act upon the reciprocating member in supplement to thedriving power during movement .in the direction of the percussion strokeand thereby developing an effective percussion stroke in the machine.

38. In a fluid pressure driven tool, the combination of a reciprocatingtool-carrying member mounted to have a retracting stroke in onedirection and a percussion stroke in the opposite direction, a drivingmeans to exert driving power upon said reciprocating tool-carryingmember during both its retracting and percussion strokes and meansconstructed to develop fluid pressure during the retracting stroke ofthe reciprocating tool-carrying member and to cause the pressure thusdeveloped, to act upon the reciprocating member in supplement to thedriving power during movement in the direction of the percussion strokeand thereby developing an effective percussion stroke inthe machine;said pressure developing means being provided with a connection throughwhich its initial supply of pressure-fluid is maintained by the drivingpower.

39. In a fluid pressure driven tool, atool carrying element, a drivingelement, means for confining between opposed walls of said elements abody of air through which the driving element drives the tool carryingelement on the working stroke of the latter, means causing thecompression of air upon the retracting stroke of the driving element,and means delivering air thus compressed between the driving and thetool carrying elements to raise the pressure of the confined body of airbetween said elements.

40. In a'reciprocating tool, the combination of a wheeled mounting bywhich the tool is advanced to its work having a re ciprocatingtool-carrying element mounted thereon, a constantly runningfluid-compressing means carried on said wheeled mounting and runningindependently of the tool carrying element, a fluid-pressure-drivenreciprocating element imparting its reciprocations to the tool carryingelement, and means whereby the reciprocating element acts directlythrough the fluid pressure medium to impart motion to the tool carryingelement in the direction and at the end of the working stroke of thelatter.

41. In a fluid pressure tool, the combination of a wheeled mounting bywhich the tool is advanced to its work, a constantly running rotarydriver carried on said wheeled mounting, a tool-carrying elementreciprocations to the tool-carrying element, Fairmont, W. Va, this 26thday of Novemand said cylinder being constructed to con-o ber, 1904.

fine a body of air between said piston and ALEXANDER PALM-ROS gtool-carrying element which cushions the 5 forward impulse transmittedfrom the pis- In presence ofton to the tool-carrying element. T. W.BOYDSTON, The foregoing specification signed at- CLARA BOYDSTON.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents Washington, D. C.

